SULFATE ADENYLATION-BIOCHEMISTRY & ENZYMOLOGY

描述（改编自申请人的摘要）：ATP硫酸化酶，来自E.大肠杆菌， 催化和构象耦合GTP水解的自由能， 活化硫酸盐合成（反应1和2）。酶是唯一的例子 将两种化学物质的自由能偶联的GTdR/靶复合物的分子量 反应.在催化循环期间， 活性位点驱动结构变化， 个人反应。这些关联事件导致了一种相互依赖性， 固定反应的化学计量，并耦合它们的自由能。的 拟议的研究将集中在这些联系事件上，并将建立 发生在GT3/靶标中的变构相互作用的范例 复合物，和自由能的构象耦合。 ATP + SO（4）<->APS + PPi（1） GTP + H（2）O <->GDP + Pi + H（+）（2） 在硫酸盐活化途径的第二步和最后一步中， ATP的γ-磷酰基转移到APS的3 '-羟基上， PAPS（反应3）。 ATP + APS <->PAPS + ADP（3） PAPS是唯一已知的代谢中的硫酰基供体。硫酰基转移， 就像磷酰基转移一样，被细胞广泛用于调节 代谢物活性在人类中，整个硫酸盐激活途径是 包含在一种酶中PAPS合成酶这个单体73 kDa 多肽催化反应1和3，并在其之间通道APS 活性位点人PAPS合成酶已被表达和纯化， 主要研究者实验室的同质性。结构 通灵系统是罕见的，并揭示了惊人的架构， 这些酶用于在它们的活性位点之间分流底物。PAPS 合成酶有望成为这些系统之一。PAPS合成酶晶体 已经获得了2.8埃的折射率。现有范式 这表明，通道效应需要大量的变构相互作用， PAPS合成酶的活性位点。Leyh博士将启动一个结构和 这个迷人的系统的功能特性。

DESCRIPTION(adapted from applicant's abstract): ATP sulfurylase, from E. coli, catalyzes and conformationally couples the free energies of GTP hydrolysis and activated sulfate synthesis (reactions 1 and 2). The enzyme is the only example of a GTPase/target complex that couples the free energy of two chemical reactions. During the catalytic cycle, allosteric interactions between the active sites drive structural changes that control the progression of the individual reactions. These linking events result in an interdependence that fixes the stoichiometry of the reactions, and couples their free energies. The proposed studies are focused on these linking events and will establish paradigms for the allosteric interactions that occur in GTPase/target complexes, and the conformational coupling of free energy. ATP + SO(4) <-> APS + PPi (1) GTP + H(2)O <-> GDP + Pi + H(+) (2) In the second and final step of the sulfate activation pathway, the gamma-phosphoryl group of ATP is transferred to the 3'-hydroxyl of APS to form PAPS (reaction 3). ATP + APS <-> PAPS + ADP (3) PAPS is the only known sulfuryl group donor in metabolism. Sulfuryl transfer, much like phosphoryl transfer, is used extensively by the cell to regulate metabolite activity. In humans, the entire sulfate activating pathway is contained in a single enzyme, PAPS synthetase. This monomeric 73 kDa polypeptide catalyzes reactions 1 and 3 and channels APS between its active-sites. The human PAPS synthetase has been expressed and purified to homogeneity in the principal investigator's laboratory. Structures of channeling systems are rare and have revealed the amazing architecture that these enzymes use to shunt substrates between their active sites. PAPS synthetase promises to be one of those systems. Crystals of PAPS synthetase have been obtained that diffract to 2.8 angstroms. The existing paradigms suggest that channeling will require extensive allosteric interactions between active sites of PAPS synthetase. Dr. Leyh will initiate a structural and functional characterization of this fascinating system.